The broad aims of the project are to determine the structure and mechanism of action of metalloenzymes. Incorporation of a catalytically essential metal ion confers on the macromolecules certain features unique to the chemistry of the metal ion and retained by the protein-bound metal ion (e.g. ESR, NMR, specific absorption and fluorescence spectra) which can be used as probes of structure and mechanism. Substitution of other metal ions for the native ion provides the opportunity to insert metals with special chromophoric properties as well as examine the role of the metal ion by determining the comparative effect on catalysis produced by closely related metal ions with slightly different solution chemistry. Detailed studies of the RNA polymerase of bacteriophage T7, the DNA polymerase of E. coli, the alkaline phosphatase of E. coli, and the carbonic anhydrase and superoxide dismutase of mammalian red cells. The methods to be employed are atomic absorption, optical spectroscopy, ESR, NMR, CD and magneto CD, and in vivo labelling of proteins with Zn65. Support for the collaborative X-ray crystallography of alkaline phosphatase is being given by preparation of single crystals and crystals of phosphate, arsenate, and phosphonate complexes.